This invention relates to a radio communication apparatus for selectively receiving a plurality of call signals indicative of a plurality of call numbers, respectively. The radio communication apparatus may be a radio paging receiver, a transceiver, or the like although description will be mainly made about the radio paging receiver.
A radio paging receiver of the type described, deals with a plurality of call numbers. The radio paging receiver is for selectively receiving call signals which carry the call numbers, respectively.
The radio paging receiver comprises a receiving circuit for receiving each of the call signals as a received signal. More specifically, the received signal is produced as a particular reception signal in response to one of the call signals that indicates one of the call numbers.
In a conventional radio paging receiver, a processing circuit is connected to the receiving circuit to process or classify the received signal into one of a plurality of individual tone signals which corresponds to the call numbers, respectively. The above-mentioned one of the individual tone signals indicates reception of the particular reception signal.
Connected to the processing circuit, a controlling circuit controls a tone generator to make the tone generator generate a particular one of audible tones as a particular tone in response to the above-mentioned one of the individual tone signals. The particular tone indicates reception of the particular reception signal. In other words, the particular tone indicates the call number of the particular reception signal.
Thus, the conventional radio paging receiver carries out not only indication of the call number of the particular reception signal but also indication of arrival of each of the call signals by the use of the particular tone. In other words, indication of the call number of the particular reception signal and indication of arrival of a certain one of the call signals are simultaneously carried out by the particular tone.
In order to avoid influence of an ambient noise, it is necessary to make the tone generator generate a loud tone as each of the audible tones. For example, each of the audible tones has a large sound pressure level which is higher than seventy-five decibels when the sound pressure level of each of the audible tones is measured at a position spaced from the radio paging receiver by thirty centimeters. That is, the radio paging receiver generates a considerably loud tone when the receiver is positioned at a comparatively quiet place.
However, a possessor of the receiver cannot stop such a loud tone until the possessor can recognize the call number corresponding to the tone in question. This is because the tone serves as both the indication of arrival of any one of the call signals and the indication of the call number of the call signal received as the particular reception signal.
Inasmuch as a long time interval is necessary to recognize the call number corresponding to the tone in question when the receiver can deal with an increased number of call numbers, a loud tone is inevitably generated for a long time. Thus, the conventional radio paging receiver unavoidably gives any trouble to those around the receiver.